Machines such as, for example, dozers, motor graders, wheel loaders, and other types of heavy equipment are used to perform a variety of earth-moving tasks. Some of these tasks requiring removal of large amounts of material can be difficult for an unskilled or inexperienced operator to achieve efficiently. For example, an unskilled operator may attempt to remove a maximum amount of material during each excavation pass, but may only be able to do so at a very slow speed. Another unskilled operator may attempt to travel quickly, but may only be able to move a very small amount of material during each excavation pass at that speed. Finding the most productive combination of load and travel speed can be complicated, especially when manually performed by an inexperienced operator. Poor productivity and low efficiency can be costly to a machine owner. Because of these factors, the completion of some tasks by a completely operator-controlled machine can be expensive, labor intensive, time consuming, and inefficient.
One method of improving the operation of a machine under such conditions is described in U.S. Pat. No. 4,423,785 (the '785 patent) issued to Kurihara et al. on Jan. 3, 1984. The '785 patent describes a load control device for a working tool of a construction vehicle. The load control device is programmed with an effective traction power versus vehicle speed curve that is associated with the particular construction vehicle and working tool. From this curve, the load control device selects a maximum productivity point having a corresponding travel speed and drive force. The travel speed and drive force are then made desired values used to automatically control operation of the construction machine. As the construction vehicle moves about a worksite and is exposed to accelerations and decelerations associated with changes in terrain, the desired values are modified. By targeting the maximum productivity point, operation of the construction machine may be improved.
Although the construction machine of the '785 patent may be capable of improving machine productivity, its use may be limited. That is, because control of the construction machine is based on a predefined curve associated with only one new machine and a single work tool configuration for that machine, the curve's accuracy may hinge on the machine's configuration and capacity remaining unchanged. And, for the same reason, the control strategy may be inapplicable to other machines or other work tool configurations having a different output capacity or to an older machine with diminished capacity.
The disclosed system is directed to overcoming one or more of the problems set forth above.